Process of detinning tin scraps and producing tin compounds.



' alloy of tin and iron, requires the applica-' OTTO K. ZWINGENBERGER, OF NEW YORK, N. Y.

PROCESS OF DETINNING LIN SCRAPS AND PRODUCING TIN COMPOUNDS.

Specification of Letters Patent. Application filed July 16, 1909. serial No. 608,041.

No Drawing.

[[0 all whom it may concern:

Be it known that I, O'r'r0 K. ZWINGEN- mesons, a citizen of the Empire of Germany, and resident of New York, in the county of New York and the State of New York, have invented certain new and useful Improvements in the Process of Detinning Tin- Scraps and Producing Tin Compounds, of which the following is a specification.

The invention is based on the chemical reaction between chloringas and metallic tin which forms tin-tetrachlorid.

The process for the'recovery of tin from tin-scraps by means of chemicals as acids,

acid salts and by means of electricity in alkaline liquids'have all the shortcomings that they require relatively much labor. The chemicals attack iron and this action on the iron increases in the degree the layer of tin decreases so that finally the process must be interrupted because it would be too diflicult and uneconomical to separate the tin products from the iron-products in order to bring the former into merchantable form. The electrolytic process with a solution of sodium-hydrate takes off very easily the upper layer of tin, butthe taking off of the layer close to the iron plate, which represents an tion of a higher electric energy whereby other metals present in the sheet-plate participate in the process and in the long run of the process the-carbonic acid gas of the air acts on the sodium-hydrate solution raising dilliculties too. The detinning of tin-scraps by means of chlorin gas is free from all these shortcomings, for the tin-scrap is handled in bundles and the process is completed in one single operation delivering the tincompounds directly in a marketable condition. The detinning by this chlorin-process is more complete than by any other process and no tin is lost in washing or while handling the detinned iron-scraps.

ilany details of the preparation of tinscraps for the detinning processes and the treatment of the detinned iron-scraps were long known.

and the like material from fat, varnish and the like impurities by treating the tin-scraps with sodi lm-hydroxid (I). R. P. 21,628.) It was early found out that both the chlorin ilready in 1883 Reinecken' destznbed lllS method of cleanlng tin-scraps latented Dec. 14, 1909.

gas and the tin-scraps must be absolutely dry tained by artificial cooling. I have now The low temperature is essential for the; success of the process and is often mainfound out that this low temperature can be Successfully maintained by giving the chlorin a larger surface of tin-scraps to work on, as the elevation of the temperature is especially caused by the action of chlorin which owing to its excessive'supply to one place works like a blast-flame and the heat generated spreads quickly all over the mass thus inviting a still greater action of the chlorin and increasing the loss as much iron may be attacked and decreasing the value of the obtained tin-tetrachlorid. I have found out that the low temperature is fully guaranteed by creating a partial vacuum in the receptacle containing the raw-material, whereby when observing a suitable connection of the receptacles the chlorin' gas is more equally distributed over the receptacles and cannot raise the temperature over a due degree.

I am aware that it has been proposed to apply low-pressure in the detinning process by ,connecting the detinning apparatus with an exhausting device. This process is used for the removal and recovery of the residue of chlorin gas and tin-tetraohlorid when all or nearly all of the tin has been dissolved so that the flow of chlorin gas upon the tin- .scrap is discontinued (Seely, U. S. P.

127,375). The method of carrying out this partpf the process consists in connecting the exit-pipe of the vessel 1, at the stage when all tin is dissolved, with the inlet-pipe of vessel 2. A similar method applies exhausting devices (Sperry, U. S. P. 872,092) especially to dry the tin-spraps before the detinning and to remove the surplus of chlorin gas and the residue of tin-tetrachlorid from the reaction vessel after finishing the deti'nning process.

It may be obvious to use exhausting devices for forwarding gases from one receptacle to another or to remove the residue of gaseous products from one vessel as demonstrated by those two processes mentioned above, but it is not obvious at all to use a partial vacuum for distributing gases over a plurality of vessels in order to moderate the heat produced by a 'hemical process and to Cir . chlorin and tin-tetrachlorin contained in pressed air in the time the workmen are difliculties and the tin will be lost. As even "detinned iron-scrap with a solution of l tion:

,sion and saving of labor.

often in the processes having the vessels sodium hydrate to sodium tannate in which improve the quality of the obtained goods simultaneously saving labor and affording like advantages. 1

Though the application of low-pressure in detinning operations is known per se the difierence between my process andthose above'is great and important because in the old style any detinning-vessel connected in series is in a diflerent stage of operation and pressure or low-pressure respectively. It is evident, that a process, in wh-ich on account of the special connection of the vessels and the equal distribution ot chlorin gas over all the vessels any of the latter-is exactly at the same stage of operation and Will be finished at the same time, is a great improvement for its easy control and the great divi- The division of work is very convenient, for it a series of for instance -12 vessels is finished at the same time the residue pf the first vessel will be driven off by comgoing to connect the other vessels with the conduit for compressed air etc. One gang of workmen is therefore kept busy all the time by emptying the detinning vessels and handling the iron-scrap until itis'ready for delivery to the smelting works. The workmen waste no time by Waitingfor the finishing of the process in a vessel as it happens connected in series thus finishing each vessel separately at an uncertain time.

The detinned'iron-scrap must be .vvashed for tworeasons. The one reason is to save the last traces of tin-tetrachlorid and the scrap from rusting. Washing with water dissolves simultaneously the'xiron-chlorid l With-the tin-tetrachlorid and from this solution tin can be recovered but with great these little quantities lost daily amount in the long run to a considerable quantity I tried several ways and found Washing the sodium-sulfate as the most suitable method to recover the last remains of tin contained as tin-tetrachlorid in the spongy layer of iron chlorid. Now this sodiumsulfate solution dissolves iron-chlorid as well as-tintetrachlorid, but the tin-tetrachlorid is precipitated out of the Washing fluid inthe form of tin-hydroxid accordingto the equa- SnCl,+4Na SO;-[-4;H O:

y p Sn(OI-I) +4NaCl+ 4NaH.SO,. This tin-hydroxid is completely precipitated by heating the washing-fluid and after filtering it from the liquid it is dissolvedin an losses of materials. other is to save the clean and bright iron- 5 y form it is much used in the cloth-printing industry. Since by the washing with sodium-sulfate the detinned iron is exposed tothe corrosive action of-sodium-bisulfate, the detinned iron-scraps are thereupon Washed with water and to be sure to neutralize the last tracesvof acid saltadhering to the bundles of detinned iron the latter are dipped in a bath of sodium-carbonate solution.

The precipitation of tin in the form of tin-hydroxid only takesplace'when' the so dium-sulfate solution is of neutral reaction. As-sodium bisultate is formed by the precipitating processthe washing fluid is neutralized bycaustic soda or quick lime before it is used for another washing-process.

.. .I will now completely describe my process;-

The bundles of tin-scrap are first submitted to a separating process provided 'the manufacturing concerns do not supply the tin-scrap with varnish and other impurities separated from those free of varnish etc. The tin-scraps are'washed in a bath of caustic soda, rinsed with Water and then dried in a drying chamber. The bundles of tin-scraps are then packed into a suitable receptacle which may be of iron, stone or brickwork and in which the action of chlorin .on the tin scrap takes place. It is the first requirement that the chlorin gas be absolutely dry and that besides the naturally required openings for the entrance andexit of the chlorin gasall other openings are duly closed in order to protect the attendants against the effects of the chlorin gas and fuming tin-tetrachlorid and to avoid The chlorin gas may through the-receptacle and leaves, if it is be used in the concentrated-or diluted form and is introduced into the receptacle at the bottom, passes not absorbed by the tin, through an opening on top of the receptacle; The tin-tetrachlorid generated by the reaction is'drained ofl' through the bottom into a collector. Special care is taken that the temperature caused by the reaction does not rise too high and steps have to be taken to keep it as low as possible. p

In order to distribute the chlorin equally overall the vesselsthe latter are joined parallel in the same Way as the elementsot a galvanic battery so thatthey have both the main-supply-pip'e and main-exhaust-pipe in common. There escapes a varying quantity of chlorin gas which depends on the degree ,to which the "detinning process has progressed. For most of the time the detinning It the process is nearly finished then a greater quantity of. chloringas will escape .ii's

' must be ready again for their turn.

The partial vacuum in the detinning vessels is maintained by a vacuum-pump. The reserve detinning vesselstak'ing up the last traces of chlorin gas are not directly connected with the vacuum-pump. For greater security againstlosses a small tower of'suitable material is inserted between the reserveQ vessels and the vacuum-pump. This tower of moderate size is filled wit-h granulatedtin or any other granulated metals, the chlorid of which is soluble, over which just enough water is running-from top "to the bottom to keep the granulated tin moist enougl'i.v

Liquids for the absorption of traces of chlorin gas are not reliable enough as such liquids, when approaching the point of saturation do not absorb chlorin gas fully and must be too often renewed, whereas a granulated metal like tin, always kept moist,

. readily absorbs the last traces of chlorin gas and besides has the great convenience, that one filling of granulated tin goes for a considerable long time. The resulting solution of tin-tetrachlorid may be made the basis of marketable products by enriching it with more tin-tetrachlorid. v

As soon as the processis finished one dctaches the collector below. the bottom, introduces compressed air through the top of the vessel whereby the remaining detinned iron-scraps are freed of the tin-'tetrachlorid vapors, and the chlorin gas is driven out too. The detinned iron-scraps are then given a wash with asodiunrsulfate solution whereby the thin layer of iron chlorid is dissolved as well'as the tin-tetrachlorid which is kept back by the spongy iron chlorid and is not always fully given off. This washing-fluid, contail'iing now both iron chlorid and tintctrachlorid, is then occasionally heated until the tin is completely precipitated in'the form of tindxydroxid, a form which allows easily its working up into marketable form. After this washing with sodium-sulfate solution the iron scrap bundles are well washed with water to remove the sodium bisulfate from the bright surface and in order to couuieract'any corrosion by this acid salt the bundles of iron-scrap are finally dipped in a bath of sodlum carbonates,

The advantages of my process are demonv strated by the following description:

The applying of a vacuum has long been. I

chemical matter. The losses sustained by this decomposition consist both in direct loss of raw material and in the inability ofproducing a pure chemical stuff the resulting products being mostly spoiled by such decomposed matter to a great extent.

7 There has come into use therefore the method of distilling such perishable chemicals under partial vacuum thereby lowering the boiling point to such a degree that the distillation goes on without decomposition.

The situation inthe' detinning process s a strikingly similar one. By maintaining the partial vacuum in the detinning vessels the chlorin gas is'in a kind of dilutedstate and the action of the chlorin gas goes min a moderate way keeping down the temperature and avoiding the generation of iron-'chlorid so that- I can determine my process as a process for distilling otl' tinundera partial vacuum by means of'chlorin gas.

The process is carried out in a 'dry state. Owing to the absence of water the chlorin as acts only on the upper layer of tin and finally on the very thin layer formed by the alloy of tin and iron reducing thus the generation of iron-chlorid to a minimum.

The partial vacuum maintained in the de- -tinning vessels throughout the process al lows most conveniently the control of the temperature and the keeping of it as low as possible. The vacuum 15 easily maintained -in the same degree over all the detinning vessels and the necessary regulations do not require much time and can be done in a very short time by a single man. This method saves therefore a good deal of labor. A most important factor is involved in the application of vacuum, as it excludes the many and most serious troubles which in case of a leak take place with the application of pressure 'to the vessels. In case the chlorin gas, in whatever form it may be used, is acting on the tin-scraps while the vessels are standing under pressure and an accident should occur the health of the attendants is exposed to the most serious danger which with great probability may result in either death or permanent injury. In the pressure process all gaseous products coming in questlon have in a to the gaseous chlorin generated in the elec trolytic cells. It is evident that. the'varu process not only avoids losses of raw-ma..

rials but is a great safeguard in regard to the health of the attendants.

' The low temperature maintained by the v acuum-process produces the tin-tetrachlolf-id in the possible greatest purity. The washiug of detinned iron-scraps with a solution of sodium-sulfate permits the recovery even the least traces of tin from the washing liuid containlng sin'mltaneously ironchlornl and tm-tetrachlorid and iurthermore the ob- 'taining of this tin in a chemical form which easily admits of its transformation into a marketable form;

The bright surface of the tin-scraps, sential for their use in the steel-furnace, is

' perfectly obtained by the wash with sodium sulfate solution and water respectively by neutralizing the last traces ofsodiumbisulfate with sodium carbonate. g

Having thus fully described'thenature of my invention, I claim as new and desire to secure by Letters Patent:

1. Process of detinning tin-scrap and thelike raw-material and recovering the tin" in form of chemical compounds and the iron' in form of iron-scrap, consisting in treating the tin-scrap or the like material. with dry chlorin gas in rcceptacies, in giving the chlorin gas the largest possible surface of tin by delivering simultaneously all of said receptacles by equally and simultaneously maintaining a partial vacuum in said receptacles during the time the action of clilorin gas on tin takes place, in removing the chlorin gas and the tin-tetrachiorid out chlorinr gas in, receptacles, in giving the the chlorin gas 1n as far as possible equal quantities int-o chlorin gas the largest possible surface of.

tin by delivering simultaneously the chlorin gas n as far as possibleequal quantities into --all of said receptacles by maintaining equally'and simultaneously a partial vacuum 1n said receptacles, 1n ]01II11]g said receptar cles ,in parallel for maintaining the partial vacuum simultaneously inzal'l vessels, in removing the chlorin gas and the tintetrachloridout of the receptacles and afterward washing the iron-scrap for collecting the last traces -of-tin-tetrachlorid and removingthe chlorid of iron from the iron-' scrap. a a

3. Process for detinning tin-scrap'and the like raw mate'rial, consisting in treating the tin-scrapjwith dry chlorin gas in a receptacle, removingafterward the chlorin gas and the residue of tin-tetrachlorid by compressed air and washing the iron-scraps with a solution o'fgsodium-sulfatc to collect the last traces of tin-tetrachlorid and removing the chlorid of iron adhering to the detinned iron-scrap LIProcess for detinning tin scrap and the ass like raw-material, consisting in treating the tin-scrap with dry chlorin gas in a receptasodium. sulfate,.treating them afterward in ,a separate vessel with a solution of sodiumsulfate and agitating the sodium-sulfate solution either" to completely collect the last traces of tin-tetrachlorid and removing the chlorid of iron from the detinned iron-scrap.

5. Process for detinning tin-scrap and,

the like raw-material, consisting in treating the tin-scrap with dry chloringasin a re-,

ceptacle. removing the chlorin gas and the residue of tin-tetrachlorid b com-J may adhere to the iron-scrap.

7. Process Iordetinnuig tin-scrap and the like rawcnaterial, consisting in treating the tin-scraps with dry chlorin gas in a receptacle, removing the chlorin gas and the residue of tintetrachlorid by compressed air,

washing the detinned. iron-scraps with a solution'ot sodium-sulfate, afterward rinsing the ironscrap with water, then dipping the iron-scrap into a bath of soda solution and in heating the sodium-sulfate bath for completely precipitating the tin in the form of tin-hydroxid from the solution.

- 8. Process for detinniiig tin-scrap and the like raw-material, consisting in treating the tin-scraps with dry chlorin gas ina receptacle, removing the chlorin gas and the residue of tin-tetrachlorid by compressed air, washing the detinned iron-scraps with a solution of sodium sulfate, afterward rinsing the ironscrap with water, then dipping the ironscrap into a bath of soda solution and re storing the neutralreaction of the sodiumsulfate washing fluid by treating it with alkalics or eartlralkalies or carbonates.

9. Process for detinning tin-scrap and the like raw-material, consisting in treating the tin-scraps with dry chlorin gas in a receptacle, absorbing the chlorin gas suppliedin excess and escaping through the exit in a irontower filled with granulated tin or other.-

metals forming soluble chlorid-compounds,

moistening such metal in the tower by introin testimony whereof I have signed my duclng Water or steam through the tower on. i name to 1115 speclfication lnthe presence of \0 top of the metal, removlng'the-ehlorm s twu FHbSCYlblIIg wltness'es.

and the residueof tin-tetrachlorid aften-fin- 7 w T A e w ishing the process .byc'ompressed air, wash- OTTO I) GDABERGLR' ing the detinned irbn for saving the last. Witnesses: Faces of tm and removlng the 11*011 chloral 1ELIA WOLF,

adhering to'the detinned lion-scrap. JOEL H. RIBETH. 

